First: If this is the wrong component for this bug, please move it to the correct one. When I use the multimedia hotkey of my Thinkpad T440s to mute the main loudspeaker, a notification sound is played (this default "pop" sound). When I unmute the sound again, no notification sound is played. IMHO this should behave the exact other way around: When I mute my speakers, I don't want them to emit any sound - so no notification sound should be played! When I unmute the speakers it's ok of them emitting a notification sound as a confirmation.
Fixed with https://phabricator.kde.org/R115:ada2f9c75019e15c37dbfdbe8a4ae42c69ec6a83